1. Technical Field
The present invention relates to a power tool. More particularly, the invention relates to a router having a main unit movable with respect to a base to finely adjust a position of a cutter, thereby adjusting a depth of a groove to be cut in a workpiece. Further, the invention relates to a portable electric router in which a stopper pole is moved with respect to the main unit to move the main unit with respect to the base to adjust the depth of the groove to be cut in the workpiece.
2. Related Art
Electric power tools called routers have been well-known for cutting a groove in a workpiece. The router comprises a base, a main unit, a cutter, and a pair of handles. The base has a sliding surface on which a workpiece slides. The base has a through hole that extends perpendicularly to the sliding surface.
The main unit is supported on the opposite surface to the sliding surface of the base. The main unit can be moved with respect to the base in a direction perpendicular to the sliding surface. A workpiece is generally contact with the sliding surface in a horizontal position. Therefore, a moving direction of the main unit is usually a direction perpendicular to the sliding surface or a vertical direction. Hence, the main unit supported over the base can be usually moved up and down with respect to the base. The main unit has two through holes in which a pair of pillar-shaped members are inserted.
The two pillar-shaped members, called columns, support the main unit to the base. These pillar-shaped members are arranged parallel to each other, each extending perpendicularly to the sliding surface. The pillar-shaped members are fixed at one end to the base. The other end portions of the pillar-shaped members are inserted in the through holes. A fastening member is provided near the through hole in the main unit. The fastening member is designed to fasten one pillar-shaped member to the main unit temporarily to prevent the pillar-shaped member from moving with respect to the main unit. While fastened by the fastening member, the pillar-shaped member is temporarily held immovable.
The main unit has two projections which extend from left and right sides of the main unit, respectively, when the sliding surface extends horizontally, contacting with a workpiece. The router has the pair of handles which are mounted on the distal ends of the projections, respectively. A user may hold the handles with hands, respectively.
The main unit incorporates an electric motor. The electric motor has an output shaft that extends to the base in a direction perpendicular to the sliding surface. The cutter is attached and secured to the distal end of the output shaft. The cutter can move through the through hole of the base downward from the sliding surface, when the main unit is moved down to the base.
A method of cutting a groove in a workpiece by using the router will be described below. The fastening member is operated, thus releasing the pillar-shaped members from the main unit, allowing the main unit to move with respect to the both pillar-shaped members. The user holds the handles with hands, respectively, and then moves the main unit to a desired position with respect to the base. The user operates the fastening member to fix the pillar-shaped members to the main unit, making the main unit immovable with respect to the base The cutter is then projected through the through holes to the workpiece by a desired distance from the sliding surface. The desired distance is the depth of a groove to be cut in the workpiece.
After setting the router in the above state, the user can hold the two handles with the hands, respectively, and move the router over the workpiece, contacting the sliding surface and maintaining the sliding surface in a substantially horizontal position. As a result, the cutter forms a groove in the workpiece because the cutter protrudes downward from the sliding surface. This type of router is disclosed in Japanese Patent Application Publication No. Hei 6-020726.
When using the conventional router described above, the user needs to hold the handles with the hands, respectively in order to support the main unit. The user then moves the main unit to a desired position with respect to the base, and protrudes the cutter by a desired distance to the workpiece from the sliding surface. Therefore, it is difficult to finely adjust the protruding distance of the cutter.
There is another method of using the router. In this method, a support member is secured to the router to support the router to an edge of a so-called router table. That is, the router is used with the base of the router being held upward in a vertical direction with respect to the main unit. The router is then supported at the edge of the router table by means of a support member. In this case, the user holds the handles with the hands, respectively, to move the main unit up and down in the vertical direction against the relatively large weight of the main unit to adjust the protruding distance of the cutter. Inevitably, it is more difficult to finely adjust the protruding distance of the cutter.
A router is proposed which has a fine-adjustment mechanism to finely adjust a moving distance of the main unit with respect to the base. In this case, the main unit needs to be moved first to a position near the desired position prior to the fine adjustment. The user must hold the handles with the hands, respectively to move the main unit. Hence, a mode of using the router need to be switched between the fine-adjusting mode in which the fine-adjustment mechanism adjusts the protruding distance of the cutter and the main-unit moving mode in which the user manually moves main unit to change the position of the main unit with respect to the base considerably. Further, if the user tries to operate the router in either one of the modes without holding the main unit, the user cannot easily move the main unit by handles, nor finely adjust the protruding distance of the cutter.
An object of this invention is to provide a power tool in which a moving distance of a main unit with respect to a base can be fine-adjusted, thereby fine-adjusting a protruding distance of a cutter from the base to a workpiece.